To demonstrate that continuous long-term recordings of the work of breathing can provide more information, compared to standard short-term recordings.
We continuously recorded the WOB (J/L/breath), power of breathing (POB [J/min]), and pressure-time index (PTP [cm H2O . sec/min) in 15 adult intubated surgical and cardiac intensive care unit (ICU) patients, after they had been mechanically ventilated for at least 24 hrs. All WOB data, cardiovascular and respiratory parameters, and ventilator settings were recorded continuously by a Novametrix Medical Systems monitor (Wallingford, CT), and saved in a central computer for analysis. The average recording time was 6 hrs for each patient, with a maximum of 9 hours. The treating physicians made all ventilatory or therapeutic changes independently of the research team.
We observed that in all patients, when there was no change in 1) clinical condition, 2) ventilator settings, 3) sedation score, 4) therapeutic protocols, and 5) in the absence of external stimulation, WOB, POB, and PTP had a tendency to decrease over time. The figure shows the fall over time of WOB, POB, PTP, in a 54-year-old man with acute pancreatitis, renal failure, anaphylactic shock, and sickle cell disease, after 24 hours of ventilatory support. The patient was intubated with an 8.0 ETT. Ventilator settings were: SIMV mode, FiO2 0.4, IMV rate 2 breaths/min, PEEP 5 cm H2O, and PSV 10 cm H2O; these did not change throughout the study.CONCLUSIONS: A possible cause for this trend may be the adjustment of the patient’s respiratory system to the ventilator.
The long-term recording of the work of breathing may better assist the clinician in understanding the changes in work due to different factors, and thus, may facilitate weaning.
E.J. Adhami, None.